Which arrangement lists the three layers of a normal soil profile?

• A. Root zone, tap soil, bedrock
• B. Sand, silt, clay
• C. Topsoil, subsoil, and root zone
• D. Topsoil, subsoil, and bedrock

Answer: (D)

Knowing how a soil profile is arranged from the surface downward is what this question tests. The top layer, topsoil, is rich in organic matter and nutrients and is where most plant roots thrive. Beneath it lies the subsoil, which stores minerals and supports deeper root growth but contains less organic matter. The final layer in a normal profile is bedrock, the solid rock beneath the soil that forms the base for the weathered materials above it. This progression from nutrient-rich topsoil to deeper, less fertile subsoil, and finally to bedrock, matches the standard soil profile structure. Terms like root zone or sand/silt/clay describe function or particle sizes rather than the official horizon sequence, so they don’t fit this question’s typical three-layer arrangement.